Subaru JDM Engines in Phoenix, Arizona
Nearly every Subaru engine enquiry here starts with a head gasket.
Subaru’s boxer engines have a specific and well-known failure mode, and it drives almost all replacement demand: head gasket failure on the naturally aspirated EJ25, particularly on earlier builds.
The families that matter are the EJ25 in the Forester, Outback, Legacy and Impreza, and the JDM-market EJ20 that comes in as an import for WRX and STI builds.
Repair or replace, on a boxer specifically
A head gasket job on a flat-four is labour-heavy because of how the engine sits in the car. The access that a conventional inline engine gives you simply is not there. That labour is the reason this decision is closer than it looks.
If the engine overheated badly, the heads may need machining as well, and at that point the cost climbs toward a used replacement. The assessment of the heads is what actually decides it, so get that done before choosing.
And if you replace: ask what has been done to the gaskets on the replacement unit and with which parts. A used EJ25 can arrive carrying exactly the same latent problem, which is the one outcome that leaves you worse off than before.
Where the EJ family boundaries sit
Naturally aspirated EJ25 variants, EJ251, EJ252, EJ253, are single-cam engines. The turbocharged EJ255 and EJ257 are twin-cam. Counting camshafts is the quickest structural check.
The FB25 changeover
From 2019 Subaru began replacing the naturally aspirated EJ25 with the FB25. The FB25 is a fundamentally different engine: it uses direct injection, a timing chain instead of a belt, and different engine management throughout.
The FB25 was designed specifically to address the EJ25's well-known head gasket problem. It is a more reliable engine in that respect, but it is not interchangeable with the EJ25 in either direction. A 2019 Forester and a 2018 Forester that look identical externally can have different engines with different parts, different labour and different costs.
Cars near that changeover year need the engine code confirmed from the block or the VIN rather than assumed from the model year. Getting it wrong is the most expensive mistake on a Subaru replacement.
Turbo models: WRX, STI and the Legacy XT
Subaru's turbocharged models use different engines from the naturally aspirated cars, and the family codes are not interchangeable with the EJ25 you find in a Forester or Outback.
The WRX uses the EJ255, a turbocharged 2.5-litre with different internals, different turbo hardware and different engine management from the NA EJ25. The STI uses the EJ257, which is a further step up in specification. Later Legacy XT models moved to a turbocharged FA20, which is an entirely different engine family again.
JDM-market EJ20 engines are a swap option for US cars, particularly popular in WRX builds. They are not a direct replacement for any US engine. The swap requires planning around engine management, wiring and supporting hardware, and is firmly in the project category rather than the repair category.
Subaru engine families
Each page covers the variants, where the code is stamped, and what changes between units of the same family.
- EJ252.5 L · Flat-four (boxer)Subaru’s 2.5-litre boxer from the Forester, Outback, Legacy and Impreza: the engine behind Phoenix’s most common Subaru replacement question, head gaskets included.
- EJ202.0 L · Flat-four (boxer)The 2.0-litre Subaru boxer from the JDM WRX and STI: imported rather than domestic, and bought almost entirely by people who want the turbocharged version.
- FA202.0 L · Flat-four (boxer), 4-cylinderThe FA20 is Subaru's modern horizontally opposed four-cylinder, co-developed with Toyota for the BRZ/FR-S, replacing the EJ20 in newer applications with direct injection.
- FB252.5 L · Flat-four (boxer), 4-cylinderThe FB25 replaced the EJ25 in naturally aspirated Subaru applications, addressing the head gasket issues that plagued the EJ series with an improved design.
Subaru vehicles
Start here if you know the car but not the engine. Each page breaks the model down by generation and trim.
- Subaru ForesterNaturally aspirated Foresters use the EJ25 and turbocharged XT models the EJ255, and head gaskets are why most owners are reading this.
- Subaru ImprezaWRX and STI models use turbocharged EJ variants that differ from each other and from the naturally aspirated cars.
- Subaru OutbackThe Outback used the EJ25 through most of its production, with the FB25 replacing it from 2013 onward, and head gaskets being the dominant reason owners investigate replacement.
- Subaru LegacyThe Legacy used the EJ25 and turbocharged EJ255 across its production, with the turbo models being the more common replacement candidates in Phoenix due to higher stress on internal components.
Check availability for your Subaru
Serving Phoenix, Mesa, Chandler, Scottsdale, Glendale, Gilbert and the wider Valley. Year, model and trim is enough to start.
Common questions
Why do Subaru head gaskets fail?
It is a well-documented issue on the naturally aspirated EJ25, and it is common enough on earlier builds that many owners encounter it. For a buyer the practical consequence is not the cause but the implication: a used replacement engine can carry the same latent problem, so what has been done to the gaskets on that specific unit is a question worth asking.
Should I repair or replace a Subaru engine?
It depends on whether the engine overheated and what that did to the cylinder heads. A gasket job is labour-heavy on a boxer, and if the heads need machining the cost approaches a replacement. Have the heads assessed first, that assessment is what makes the decision, not the mileage.
What is the difference between the EJ25 and the FB25?
The EJ25 is the naturally aspirated engine Subaru used in the Forester, Outback, Legacy and Impreza for many years. The FB25 replaced it from 2019. The FB25 uses direct injection, a timing chain rather than a belt, and was designed to fix the EJ25's head gasket problem. They are not interchangeable in either direction.
Can I use a JDM EJ20 in my US Subaru?
It depends on the application. JDM EJ20 engines are a common swap option for US-market WRX and STI builds, but they are not a drop-in replacement for any US engine. The swap requires attention to engine management, wiring, turbo hardware and supporting systems. It is a project, not a repair, and should be planned as one.
Related pages
- EJ25 EngineSubaru’s 2.5 boxer, head gaskets included.
- EJ20 EngineThe 2.0 Subaru boxer from the JDM WRX and STI.
- FA20 EngineSubaru's modern 2.0 boxer, co-developed with Toyota for the BRZ.
- FB25 EngineSubaru's 2.5 boxer that replaced the EJ25 in naturally aspirated applications.
- Subaru ForesterEJ25 head gaskets, and whether to repair or replace.
- Subaru ImprezaWRX and STI use different turbocharged engines.
- Subaru OutbackEJ25 and FB25 boxer engines, with head gasket failure the dominant replacement reason.
- Subaru LegacyEJ25, EJ255 turbo, FB25 and FA20 across generations, with turbo models the more common replacement candidates.
- EJ25 EngineSubaru’s 2.5 boxer, head gaskets included.
- Subaru ForesterEJ25 head gaskets, and whether to repair or replace.
- Repair or Replace Your EngineWhether to spend anything at all, before deciding what to spend it on.
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